1. Field of the Invention
The present invention relates to the field of extracorporeal treatment of blood by dialysis and/or by ultrafiltration. More particularly, the invention relates to a hydraulic circuit for an artificial kidney in which the dialysis-liquid circuit includes an ultrafilter intended to rid the dialysis liquid of microorganisms and possibly pyrogenic elements which it might contain.
2. Description of the Related Art
With the development of high-permeability haemodialyzers, there has been increased interest in the use of dialysis liquid having good biological properties to protect against blood contamination which may occur if portions of the dialysis liquid enter the blood stream. While exchanges in a haemodialyzer during blood purification are intended to only occur from the blood compartment toward the dialysis-liquid compartment, the possibility remains of having, on the contrary, a transfer from the dialysis liquid towards the blood. This may occur either by diffusion or by convection in situations where the pressure in the dialysis-liquid compartment becomes greater than the pressure in the blood compartment.
U.S. Pat. No. 4,834,888 discloses an artificial kidney comprising a filter for in-line sterilization of dialysis liquid before its entry into the haemodialyzer. According to this document, the filter used for sterilizing the dialysis liquid comprises two compartments separated by a membrane capable of retaining germs. The liquid coming from a dialysis-liquid source is completely filtered through this filter before entering the haemodialyzer. In order to avoid filter clogging, the compartment connected to the dialysis-liquid source is rinsed at the end of each haemodialysis session, and may also be rinsed during a session as well.
For this purpose, this compartment has an output connected to a line for draining the used dialysis liquid coming from the haemodialyzer. During the filter-rinsing phase, sterilizing the liquid by filtration is stopped, and the liquid entering the filter then sweeps along the surface of the membrane in order to detach the germs and pyrogenic elements which are deposited thereon. Thereafter, the liquid directly rejoins a line for draining the used dialysis liquid.
In order to check the integrity of the membrane of this sterilization filter, this document describes a specific test performed between two dialysis sessions. This test involves introducing air into at least one part of the dialysis-liquid circuit, and can therefore only be performed when the haemodialyzer is disconnected from the dialysis apparatus.
Thus, the device described in this document has the drawback of not allowing the integrity and efficiency of the membrane of the filter to be checked during use.